1. Field of the Invention
This invention relates to a high-pressure gas processing apparatus for performing hot isostatic pressing (HIP), high-pressure gas oxidation or nitration, or washing by use of a fluid in super-critical state, or a heating pressure processing apparatus employed for a solid workpiece which is to be batch processed. More particularly, it relates to an apparatus for processing a plate-like workpiece such as Si wafer one by one in a short cycle.
2. Description of the Related Art
In the manufacture of Si semiconductor or ULSI, recently, a so-called sheet-by-sheet type of processing wafers one by one in a cycle time of several minutes is increasingly dominant from the viewpoint of productivity and quality management. On the other hand, the batch type process using high-pressure which is most widely applied in industry is HIP method (hot isostatic pressing method). However, this HIP method generally requires 3-5 hours for one cycle even in a short-time processing with a small-sized apparatus.
In the application of the process utilizing a high-pressure gas to the single-wafer processing of semiconductors, shortening of cycle time is an important subject. Although the ratio of time occupied by a step such as pressurization and heating is high in the process itself, the time required for loading and unloading the Si wafer which is the workpiece also accounts for an extremely high ratio.
In this connection, an HIP apparatus used for general HIP method has no hindrance even if the loading and unloading of the workpiece requires a time of the order of several tens minutes, because the whole cycle time is on the order of several hours or more.
For a high pressure apparatus for processing Si wafers sheet by sheet, the loading and unloading mechanism of workpiece which requires much time as in the HIP apparatus can not be adapted, and an apparatus shown in FIG. 6 is proposed as a pressure recess-filling apparatus for interconnection film (Japanese Patent Laid-Open No. 7-502376).
Japanese Patent Laid-Open No. 7-502376 proposes a processing system comprising a plurality of skin parts (high pressure vessel components) 100, 101; first means 102, 103 for pressing the skin parts 100, 101 so as to mutually contact, the skin parts 100, 101 being shaped so that they are pressed and closed by the first means 102, 103 to form a sealing space 104 for a workpiece W; second means 105 for supplying a pressurized gas of atmospheric pressure or more to the internal space 104 in order to process the workpiece W by exposing the workpiece W to a high pressure; and means 106 for exhausting the pressure vessel.
Namely, referring to FIG. 6, in this conventional technique, the high pressure vessel parts 100, 101 forming the sealing space 104 for housing a workpiece (Si wafer) are divided substantially on the sides of the workpiece W, so that the workpiece W is moved in and out sideways through a passage 107 by the narrow divided space, and this structure is suitable to load and unload a thin plate-like workpiece one by one within a short time with a high-pressure gas.
Although a large subject in the structure for opening and closing the high-pressure vessel in this way is the gas sealing structure of the divided part, it is attained in this conventional technique by pressing a specific sealing structure part by the first means (gas pressure and hydraulic rams).
To press the high-pressure vessel member by gas pressure, particularly, it is proposed that the first means comprises an actuator 103 for moving one of the skin parts, and the second means 105 is arranged so as to supply a pressurized gas to the actuator for the operation of the actuator 103. This supposingly means that the pressure receiving area of the ram of the first means for supplying the pressurized gas is set larger than the axial sectional area of the space for sealing the workpiece, whereby the seal part of the sealed space part is regularly in the pressed state during the execution of the processing by the pressurized gas.
In FIG. 6, denoted at 110 is a yoke, which is cylindrically formed and has upper and lower plugs 111, 112 screwed to the upper and lower parts thereof.
It may be said that the structure of the conventional technique disclosed in Japanese Patent Laid-Open No. 7-502376 outlined in reference to FIG. 6 is suitable for the single-wafer processing of a plate-like workpiece as Si wafer by use of a high-pressure gas, but this structure has the following problems:
1) Since a heat source such as heater is housed in the high-pressure vessel in processing at high temperature, the temperature of the seal part is raised, and the stability of the seal is lost when the processing is performed for a long time or in a cycle of a number of times, although no problem arises in processing at about room temperature. In order to avoid this, a specific sealing structure mainly composed of metal is adapted in the conventional technique.
Namely, a seal 109 for the internal space 104 moves a lip formed in the upper part of the skin part 101 to the outside and firmly presses it to the skin part 100 in the seal surface to deform the lip so that the strength of the seal is increased in proportion to the raised pressure of the sealing space 104 (referred to the bottom line of the right upper column to the fifth lines of the left lower column, page 4 of the gazette thereof).
However, the sealing by the deformation of the lip has a subject that the lip is plastically deformed when the processing is performed in a cycle of a number of times, and the sealing function can not be exhibited as soon as the plastic deformation is caused.
Further, the plastic deformation of the lip also introduces a subject that the skin part itself must be replaced to ensure the sealing function since the lip is integrated to the skin part 101.
2) The conventional technique has two pressing means (first means) of the hydraulic actuator 102 and the gas pressure actuator 103 in order to mutually close a plurality of vessel components (skin parts) 100,101. In this case, however, a high pressure substantially equal to the pressure within a processing chamber (internal space) 104 is generated by the hydraulic actuator 102 together with the other gas pressure actuator 103 to enhance the probability of causing a trouble such as pressure leak. This can not be said to be preferable from the viewpoint of safety as well as it leads to a reduction in reliability of the apparatus.
3) The conventional technique is designed, as an example, so that the gas in the processing space 104 is carried into the actuator 103 through a valve 108 to produce a force for closing the high-pressure vessel in the actuator 103 having a pressure receiving area larger than the axial sectional area of the processing space 104. However, this means that the gas after use is passed through the inner part of the actuator 103, which brings on the entrainment of the dust resulted from the wear of the seal member within the actuator into the recovered gas, and a question is left for the recycle of the gas.
Namely, although it is allowed to dispose the gas (non-recovery type) when the processing frequency is less, recovery type such as forced recovery or differential recovery is adapted for production from the viewpoint of economic property. In this case, the dust is included in the recovered gas, introducing the danger of causing a contamination when transferred to the processing space.